1. Field of the Invention
The present invention relates to an electronic paper display device and a method of manufacturing the same, and more particularly, to an electronic paper display device, capable of having high image stability and uniformity and expressing various shades, and a method of manufacturing the same.
2. Description of the Related Art
A shift in information exchange and sharing methods is currently in demand, corresponding to modern society's requirement for a new information delivery paradigm. To meet this demand, the development of technologies associated with flexible electronic paper has recently been accelerated and are now entering the phase of commercial development.
Compared with existing flat display panels, an electronic paper display requires relatively low manufacturing costs, and is far superior in terms of energy efficiency since it is operable even with a very low level of energy due to the needlessness of backlighting or continuous recharge. Furthermore, electronic paper enables a high definition display, provides a wide viewing angle, and is equipped with a memory function that retains the display of letters (characters) even when unpowered. The above-described advantages make electronic paper applicable in a wide variety of technical fields, such as electronic books having paper-like sheets and moving illustrations, self-updating newspapers, reusable paper displays for mobile phones, disposable TV screens, and electronic wallpaper. There is a massive potential market for such electronic paper.
A technical approach for the implementation of electronic paper may be roughly divided into four methods: a twist-ball method, an electrophoretic method, a quick response-liquid power display (QR-LPD) method, and a cholesteric liquid crystal display method. Here, the twist ball method involves rotating spherical particles, each having upper and lower hemispheres having opposite electrical charges and different colors, by using an electric field. As for the electrophoretic method, colored charged particles mixed with oil are trapped in micro-capsules or micro-cups, or charged particles are made to respond to the application of an electric field. The QR-LPD method uses charged powder. The cholesteric liquid crystal display method uses the selective reflection of cholesteric liquid crystal molecules.
As for the twist-ball method, cells are filled with a transparent medium, and twist balls, each having opposite electrical charges and colored with different colors, for example black and white, are disposed in the transparent medium. Each twist ball, when receiving voltage, rotates such that the part of its body having an opposite polarity to the received electric charge faces the front. In such a manner, black and white are displayed.
However, the above-described structure displays only two states of black and white all of the time, and thus has limitations in expressing a variety of shades (i.e., tones).